Anti-roll system with tilt limitations

ABSTRACT

An anti-roll system for turn compensation in a vehicle generates a differential hydraulic signal in which a pressurizing potential corresponds to a first curve direction and a complementary return hydraulic potential. The system includes a pair of rear wheel cylinder and piston assemblies and a pair of front wheel cylinder and piston assemblies. A hydraulic circuit is connected to conduct the pressurizing potential to move the pistons in a first rear wheel cylinder and piston assembly and a first front wheel cylinder and piston assembly, while conducting the return signal to move the pistons in second front wheel cylinder and piston assembly and a second rear wheel cylinder and piston assembly. A hydraulic conductor directly connects corresponding ends of the rear wheel cylinder and piston assemblies to provide a hydraulic conduction between those assemblies in response to conduction of the differential hydraulic signal. A tilt limitation feature is provided in the front wheel cylinder and piston assemblies and is connected to the hydraulic circuit for limiting the maximum displacemnt of the pistons in the rear and front wheel cyilnder and piston assemblies. In a vehicle, the system reacts to a turn by causing the front and rear wheel cylinder and piston assemblies to tilt the vehicle in a direction to counteract the vehicle rolling force caused by the turn. The tilt-limitation element operates to limit the amount of tilt produced by the system of the invention to counteract vehicle roll force.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 07/563,048, filed Aug. 6,1990, now U.S. Pat. No. 5,040,823 which is a continuation-in-part ofapplication Ser. No. 07/397,723, filed Aug. 23, 1989, now U.S. Pat. No.4,966,390.

BACKGROUND OF THE INVENTION

The present invention relates to a vehicle anti-roll system, and moreparticularly, to a hydraulically-operated anti-roll system which limitsthe amount of tilt induced in a vehicle to counteract turn-induced roll.

For the purpose of establishing the general environment in which theinvention operates, it is asserted that a vehicle such as an automobileconsists of a body, four tires, two front and two rear, a frame withaxles for mounting the front and rear wheels, and a suspension forconnecting the vehicle body to the axles.

When a vehicle turns, the suspension permits the vehicle body to rotateslightly about its longitudinal axis in response to the rolling forceexerted on the body during the turn. Typically, vehicle passengersexperience this effect as a tilt of the vehicle body, with the side ofthe body on the outside of the curve being relatively lower than theside of the body on the inside. Further, the vehicle body tends to pitchforward so that the front of the body is relatively lower than the rear.The pitch and roll combine to incline the vehicle body toward the frontcorner on the outside of the turn.

Anti-roll systems are known in the art which counteract vehicle roll byproviding a lifting force acting between the vehicle body and suspensionon the outside of the curve or a vehicle lowering force acting betweenthe body and suspension on the inside turn side of the vehicle. Someanti-roll systems in the art provide complementary lifting and loweringforces simultaneously.

U.S. Pat. No. 3,752,497 of Enke et al illustrates an anti-roll system inwhich complementary lifting and lowering forces are applied. In the Enkeet al patent, two sets of complementary lifting and lowering forces areprovided, one set to the front wheels, and one set to the rear.

In U.S. Pat. No. 3,820,812 of Stubbs, an anti-roll system includes twoseparate assemblies, each working on the front and rear axles on arespective side of a vehicle. Each assembly provides a lifting orlowering force to its respective side, without reference to the actionof the other assembly.

U.S. Pat. No. 3,885,809 of Pitcher illustrates an anti-roll system inwhich two separate correction units on opposite sides of the vehicleprovide lifting and lowering forces to counteract roll. The Pitcheranti-roll system also includes a lift limitation assembly interconnectedwith the anti-roll system components and serving the rear of thevehicle.

U.S. Pat. No. 4,345,661 of Nishikawa provides a correcting force to oneside of a vehicle to counteract turn-induced roll.

My U.S. Pat. No. No. 4,589,678 operates on the front wheels tocounteract roll. It also provides limitation of front wheel correctionby means of a piston controlled hydraulic line operating between ahydraulic reservoir and a cylinder and piston assembly.

All of these existing anti-roll systems utilize hydraulic circuitry andcomponents for generating lifting and lowering forces. In each case, anelement corresponding to a cylinder and piston assembly is positioned ata vehicle wheel and acts between the wheel and the vehicle body bymoving a piston within a cylinder. Movement of the piston toward the topof the cylinder compresses the assembly's longitudinal profile andexerts a lowering force by drawing together the vehicle body and thewheel. Movement of the piston downwardly in the cylinder spreads theassembly longitudinally and exerts an erecting force which separates thebody and the wheel. The operations of a plurality of such assemblies arecoordinated by hydraulic circuitry. The circuitry reacts to roll forcesby developing hydraulic signals in the form of pressurized hydraulicfluid, and delivering those signals in appropriate configurations to thecylinder and piston assemblies. None of the instances cited aboveprovides a closed hydraulic circuit which connects all four front andrear cylinder and piston assemblies into an integrated anti-roll systemin which all of the parts act cooperatively and in response to a singlehydraulic signal. Beyond not teaching this combination, these referencesfurther do not suggest the joinder of such an anti-roll system with atilt limitation feature which limits the degree of correcting tiltdeveloped at all four wheels to counteract vehicle rolling. Neither dothese references illustrate shock absorbency internal to the hydrauliccomponents of an anti-roll system.

SUMMARY OF THE INVENTION

The inventor has observed that the counteracting response of ahydraulically-actuated anti-roll system to vehicle roll forces ismeasureably enhanced by provision of the capability, on each side of thevehicle, to limit the amount of tilt correction induced by the system.

The invention is a system for roll compensation in a vehicle havingfront and rear wheels, means for rotatably supporting these wheels, avehicle body, and a suspension connecting the body and the wheels. Theanti-roll system of the invention includes a valved hydraulic signalgenerator for providing a differential hydraulic signal indicative ofvehicle roll. The differential hydraulic signal is defined by apressurizing hydraulic potential corresponding to a first turn directionand a return hydraulic potential corresponding to a second turndirection. A first pair of cylinder and piston assemblies are providedfor roll correction at the rear wheels, and a second pair of cylinderand piston assemblies are provided for roll correction at the frontwheels. The system includes a hydraulic circuit connected to the valvedhydraulic signal generator and to the rear and front wheel cylinder andpiston assemblies for conducting the differential hydraulic signal toall of the cylinder and piston assemblies. In conducting the hydraulicsignal, the circuit provides the pressurizing potential of the hydraulicsignal to move the pistons in a first front wheel assembly and a firstrear wheel assembly in a first correcting direction, while providing thereturn potential to move the pistons in the second front wheel assemblyand the second rear wheel assembly in a second correcting direction. Ahydraulic conductor directly connects corresponding ends of the rearwheel cylinder and piston assemblies to support hydraulic conductionbetween these assemblies in response to conduction of the differentialhydraulic signal to all of the cylinder and piston assemblies. Thesystem includes a tilt-limitation means connected to the hydrauliccircuit for limiting the maximum displacement of the pistons in thefront wheel cylinder and piston assemblies which limits the amount ofroll correction afforded by the system.

A principal object of this invention is to provide an improved anti-rollsystem for a vehicle.

A distinct advantage of the described anti-roll system is found in thelimitation of the amount of corrective tilt introduced.

Other features of this invention, described below, also permit standardshock-absorbing suspension functions to be performed in response tovertical disturbances, such as jounce and rebound, without disturbing,or requiring operation of, the anti-roll function of this invention.

Other objects and distinct advantages of this invention will becomeevident when following description is read with reference to thebelow-described drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a hydraulic circuit representation demonstrative of a firstembodiment of the invention.

FIG. 2 is a schematic diagram illustrating control of the solenoid valveof FIG. 1.

FIG. 3 is a side cutaway view illustrating a rear wheel cylinder andpiston assembly used in the embodiment of FIG. 1 with an internal,hydraulically-operated shock absorption provision.

FIG. 4 is a side cutaway view showing a front wheel cylinder and pistonassembly used in the embodiment of FIG. 1 with an internal,hydraulically-actuated shock absorption provision.

FIG. 5 illustrates a damper assembly interposed between the two rearwheel cylinder and piston assemblies of FIG. 1.

FIG. 6 illustrates a second embodiment of the

FIG. 7A is a side cutaway view illustrating a front wheel cylinder andpiston assembly used in the embodiment of FIG. 6.

FIG. 7B is a perspective view of a floating piston in the assemblyillustrated in FIG. 7A.

FIG. 8 is a side cutaway view illustrating a rear wheel cylinder andpiston assembly used in the embodiment of FIG. 6.

FIG. 9 is a side cutaway view of a back pressure valve used in theembodiment of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the schematic representation of an automobileincludes a pair of front wheels 10 and 12, a pair of rear wheels 14 and16, and a frame with front axles for rotatably mounting the front wheels10 and 12. The front axles include attachment points 17 and 18. Theframe also includes rear axles for rotatably mounting the rear wheels 14and 16, the rear axles having real axle mounting points 20 and 22. Theframe, the vehicle body which is attached to the frame, and thesuspension system which is attached to the body and to the frame, arenot illustrated explicitly in FIG. 1. However, the mechanicalinterconnection of these parts with those illustrated in FIG. 1 andalready described above is well known to the skilled artisan.

A hydraulic signal generator includes a conventional hydraulic pump 30that continuously pumps hydraulic fluid under pressure. In thedescription which follows, the pumped, pressurized hydraulic fluid isreferred to as a "differential signal" and includes complementarypressurizing (P) and return (R) potentials provided, respectively,through hydraulic lines 31 and 32. The hydraulic pump 30 is connectedthrough the lines 31 and 32 to a conventional solenoid-operated,hydraulic spool valve 35, which includes a spool (not shown) andsolenoid coils 36a and 36b for positioning the spool. The valve isanchored to the frame. The valve 35 can comprise, for example, astandard, electrically actuated, double acting, four-way free flowdevice which receives and forwards the R and P potentials produced bythe hydraulic pump 30 with a polarity determined by the position of thespool 36. As is known, the spool can be moved within the valve 35 from arest position in either of the directions indicated by the arrow A. Atthe rest position, the spool blocks the hydraulic signal from beingtransmitted by the valve. Movement in one direction provides thepotentials P and R in one polarity. Movement of the spool in theopposite direction reverses the polarity of the potentials.

The valve 35 provides the differential hydraulic signal through ports 40and 42. Hydraulic lines 50, 51, and 52 are connected in common to port40 at node connector 53. Hydraulic lines 60, 61, and 62 are connected incommon to valve port 42 through the node connector 63. A first frontwheel cylinder and piston assembly 70 includes a cylinder 71 a pistonassembly 72 and a piston shaft 73. The piston shaft 73 is connected atone end to the right front portion of the vehicle body at 26a. Thecylinder 71 is connected to the right front axle at 17. The cylinder 71includes an upper port 74, and lower port 75, and a position-sensingport 76 located between the ports 74 and 75. In the left front of thevehicle is provided a cylinder and piston assembly 80 having a cylinder78, a piston assembly 79, and a piston shaft 81. The cylinder 78 isconnected to the left front axle at 18, while the piston shaft 81 isanchored to the left front of the vehicle body at 26b. The cylinder 78has upper port 83, lower port 85 and position-sensing port 86.

The right front cylinder and piston assembly 70 is connected at itsupper port 74 to the hydraulic line 50, at its lower port 75 to thehydraulic line 62, and at its position-sensing port 76 to a hydraulicline 55, which is connected to the return R line of the hydraulic pump30. Similarly, the cylinder 78 is connected at its upper port 83 to thehydraulic line 60, at its lower port 85 to the hydraulic line 52 and itsposition-sensing port 86 to the hydraulic line 65, the hydraulic line 65being connected at 66 in common with the line 55 to the return line 32port of the hydraulic pump 30.

A pair of rear wheel cylinder and piston assemblies 90 and 100 aredisposed at, respectively, the right rear and left rear of the vehicle.The assembly 90 includes a cylinder 91 in which is disposed a piston 93connected to a piston shaft 92. The piston shaft 92 is anchored at 20 tothe right rear axle of the vehicle. The cylinder 91 is connected to thebody of the vehicle at 94. The left rear cylinder and piston assembly100 includes a cylinder 101, a piston 103, and a piston shaft 102. Thepiston shaft 102 is anchored to the left rear axle at 22, while thecylinder 101 is anchored to the left rear of the vehicle body at 104.

The cylinder and piston assembly 90 has a lower hydraulic port 97connected to the hydraulic line 51, and a lower hydraulic port 97. Theleft cylinder and piston assembly 100 has a lower hydraulic port 107connected to the hydraulic line 61, and an upper hydraulic port 105connected through hydraulic circuit 109 to the upper port 95 of theassembly 90.

Reference to FIG. 2 will provide an understanding of how thesolenoid-driven valve 35 operates. The solenoid valve 35 is anchored tothe vehicle body and generates a hydraulic signal for tilt correction inresponse to operation of the steering mechanism of the automobile inwhich the system of FIG. 1 is mounted. In this regard, the steeringmechanism is conventional and includes a steering rack 121 which isstationarily attached to the vehicle. Steering is provided by the tierods 122 and 124, each connected to a respective front wheel. For aright turn, the tie rod 122 is extended, while the rod 124 is retracted,causing the wheels 10, 12 to pivot toward the right. Correspondingly,for a left turn, the tie rod 124 extends, the tie rod 122 retracts,causing the wheels 10, 12 to pivot to the left. A control plate 129 isattached to the tie rod 122 to move with it and to provide an indicationof turn direction. A preferred alternative is to locate the controlplate on the steering column, which provides immediate indication ofturn direction. A pair of proximity sensors are stationarily mounted tothe vehicle body, adjacent the plate 129, to sense its position and toprovide sense signals to a pair of relays 133 and 135, respectively. Therelays 133 and 135 are connected to the solenoid coils 36a and 36b,respectively, of the solenoid valve 35.

When the vehicle is traveling in a straight line, the proximity sensor129 will be adjacent both of the sensors 30 and 132, deactivating bothof the relays 133 and 135. In this case, the solenoid coils are inactiveand the valve spool is in a neutral position which blocks provision ofthe P and R potentials to the ports 40 and 42. A right-hand turn willmove the plate 129 away from the sensor 130, activating the relay 133,and through it, the solenoid coil 36a. This will configure the solenoidvalve 35 to provide the pressurizing signal potential through the port42 and the return potential of the hydraulic signal through the port 40.Conversely, during a left-hand turn, the plate 129 moves away from thesensor 132, activating the relay 135, and through it, the coil 36b. Thisprovides the pressurizing potential of the hydraulic signal through theport 40 and the return potential through the port 42.

Returning to FIG. 1, it is asserted that, as the vehicle executes aleft-hand turn, the centrifugal forces generated tend to roll thevehicle body clockwise on its longitudinal axis, raising the inside(left) edge, and lowering the outside (right) edge of the body. As aresult, the right-hand cylinder and piston assemblies 70 and 90 arecompressed, while the left-hand assemblies are expanded. This meansthat, on the right-hand side, the pistons 72 and 93 move downwardly andupwardly, respectively, in their cylinders. Correction requiresreversing these directions On the left-hand side of the vehicle, thepistons 79 and 103 move up and down, respectively, in their cylinders;correction requires reversal of these movements. The anti-rollcorrection provided by this invention will configure the hydraulicsignal discussed above in such a manner as to provide hydraulic signalcomponents to the assemblies 70 and 90 to counteract their compression,while providing hydraulic components to the assemblies 80 and 100 tocounteract their expansion.

When the turn direction sensors 130 and 132 indicate that vehicle inwhich the system of FIG. 1 is mounted makes a left-hand turn, the relays133 and 135 configure the value 35 such that the pressurizing potentialis provided at the port 42 and the return potential at the port 40 ofthe valve 35. With the left-hand turn, the right-hand side of thevehicle rotates toward the ground, compressing the assemblies 70 and 90.The pressurizing potential of the hydraulic signal is provided, in theright-hand side of the vehicle, to the bottom port 75 of the assembly70. At the same time, the return potential of the hydraulic signal isprovided to the upper port 74 and lower port 97 of the right-handcylinder and piston assemblies 70 and 90, respectively. Considering theright front assembly 70, the return potential at the upper port 74permits the piston 72 to move upwardly in the cylinder 71. Thispotential is complemented by the pressurizing potential provided throughthe port 75, which pushes the piston 72 upwardly. Similarly, in theright rear cylinder and piston assembly, the return potential isconducted through the signal line 51 to the assembly 90 through the port97, which permits the piston 93 to be pushed downwardly in the cylinder91.

Continuing with the description of the right-hand turn correction, onthe left-hand side of the vehicle, the pressurizing potential isconducted to the top of the piston 79 in the assembly 80, and to thebottom of the piston 103 in the assembly 100. The return potential isconducted to the bottom of the cylinder 79 in the assembly 80. With thepiston 79 receiving the pressurizing potential on its top surface andthe return potential on its bottom face, the piston will be moveddownwardly in the cylinder 78, thereby compressing the assembly 80.Similarly, the pressurizing potential delivered to the bottom of thepiston 103 through the port 107 will move the piston 103 upwardly in thecylinder 101, thereby compressing the assembly 100.

Completing the description of the circuit of FIG. 1, during theleft-hand turn, upward movement of the piston 103 will displacehydraulic fluid from the upper portion of the cylinder 101 into theupper portion of the cylinder 91 by the path 105, 109, 95. This willtransfer the pressurizing potential to the upper surface of piston 93,thereby complementing the downward motion of the piston resulting fromintroduction of the return potential through the port 97.

For an understanding of the tilt limitation feature, recall that thereturn potential is provided to the position-sensing ports 76 and 86.The return potential will be introduced only when the respective pistonhas undergone a sufficient downward displacement. Upward displacement ofthe piston of a front wheel cylinder and piston assembly will notuncover the assembly's position sensor port.

Therefore, continuing with the left-hand turn explanation, the left-handturn will tend to compress the right-hand cylinder and pistonassemblies, resulting in a relative downward movement of the piston 72within the cylinder 71 and an upward movement of piston 79 in cylinder78. However, at the time that the left-hand turn is initiated, thecorrective action of the anti-roll system described heretofore exerts acompressing correction on the left-hand assemblies 80 and 100. Thecompressing correction moves the piston 79 downwardly in the cylinder78. When the piston 79 has undergone a sufficient downward displacement,the return potential is introduced into the upper portion of thecylinder 78 through the position sensing port 86. This "short-circuits"the return and pressurizing potentials of the hydraulic signal in thecylinders 78, 91, and 101 thereby preventing any further roll correctionin either the left- or right-hand cylinder and piston assemblies. Thiseffectively limits the amount of tilt which the system introduces tocorrect the roll experienced in the left-hand turn.

In operation, correction is introduced into the system any time thevalve 35 is actuated in response to a change of steering angle from aneutral position. Thus, correction "leads" or "anticipates" slightly theroll of the vehicle. As the turn begins in response to steering, theroll force comes into effect. The roll and correction forces are kept inbalance by the position sensing ports whose actions tend to keep thevehicle body level in a turn.

The skilled artisan will appreciate that the just-given explanation forleft-hand turn correction, when reversed, will counteract the rollintroduced by a right-hand turn.

After a turn has been completed, the steering assembly is returned toits neutral or straight-ahead configuration, thereby closing thesolenoid valve 35, removing the return and pressurizing potentials ofthe hydraulic signal from the ports 40 and 42. This results in a returnof the cylinder and piston assemblies 70, 80, 90 and 100, to theirneutral positions. In the neutral positions, the pistons 72 and 79 arepositioned in their respective cylinders at locations which cover theposition-sensing ports of the cylinders.

FIG. 3 illustrates construction details of the rear wheel cylinderpiston assemblies which will provide an understanding of how theyoperate to provide shock absorption, while also providing anti-rollcorrection. The rear wheel cylinder and piston assembly 100 isillustrated with the understanding that the illustration and thefollowing explanation apply also to the assembly 90. The assembly 100includes the cylinder 101 in which the piston 103 moves longitudinally.The piston 103 includes a piston body 200 with two through ports 201 and202 which open completely through the body 200 between its upper andlower faces. Two valve springs 207 and 210 are provided on the lower andupper faces, respectively, of the piston body 200. The spring 207 coversand closes the lower end of the port 201, while the spring 210 coversand closes the upper end of the port 202. The spring 207 has an orifice208 which communicates with the port 202, while the spring 210 has anorifice 211 which communicates with the port 201. Shock absorption isprovided when the piston shaft 102 is displaced either up or down as therear wheel to whose axle it is attached encounters a bump or a pothole.Assuming a bump, the shaft 102 transfers an upwardly-directed shockdisplacement to the piston 103. If the piston were solid, theincompressibility of the hydraulic fluid with which the cylinder 101 isfilled would prevent the piston moving, assuming no complementarydisplacement of the piston in the opposite rear wheel cylinder andpiston assembly. However, the upward force exerted on the piston 103causes a relative displacement of hydraulic fluid downward through thethrough port 201 against the valve spring 207. Although the spring 207closes the lower opening of the port 201, the spring will give way fromthe opening in response to the relatively downwardly-moving column ofhydraulic fluid, thereby permitting the fluid to flow through the port201. This permits the piston 103 to move upwardly in the cylinder 101.Similarly, downward motion of the piston in response to a sharp movementof the piston shaft 102 is permitted by movement of hydraulic fluidupwardly through the through port 202 against the spring 210. Theinventor, recognizing the need to damp piston movement resulting fromjounce (bumps) differently than piston movement resulting from rebound(potholes), has provided a spring constant for the spring 210 which ishigher than the spring constant for the spring 207. Relatedly, thespring 210 may be thicker than the spring 207. During cornering, whenthe fluid is circulated through the ports 107 and 105, the spring 210provides a compressing force that is greater than the extending force ofthe assembly 90. This pulls the inside rear corner of the vehicle down,counteracting the natural tendency of the vehicle to pitch diagonally,down at the outside front end and upwardly at the inside rear.

FIG. 4 illustrates construction details of the front wheel cylinder andpiston assemblies, which will provide an understanding of how theyoperate to provide shock absorption, while also providing an anti-rollcorrection. FIG. 4 illustrates in greater detail the assembly 80, withthe understanding that the details of FIG. 4 are also found in the otherfront wheel cylinder and piston assembly 70. In the cylinder and pistonassembly 80, the piston 79 comprises an assembly including a lowerpiston 300 fixed to the shaft 81 by a nut 302. The lower piston 300 hasan disc configuration through which fluid access is provided by ports300a and 300b. A non-metallic piston ring 303 positions the fixed piston300 against the inner wall of the cylinder 78. A foam accumulator 305 isconcentrically positioned on the shaft 81 above the fixed piston 300. Arubber washer 307 is placed at the bottom of the fixed piston. Disposedabove the fixed piston 300 is a "floating" piston 309, which has anupside-down, open cup-like configuration. A metallic piston ring 311seals the outer surface of the floating piston 309 against the innersurface of the cylinder 78. An upper rubber washer 312 provides afluid-resistant seal between the shaft 81 and the central bore of thefloating piston 309 through which the shaft 81 extends. A lower rubberwasher 313 also provides a fluid-resistant seal between the shaft 81,and the central bore of the floating piston. A rigid annular retainer inthe form of a metal disc 318 is attached to the shaft 81 to provide anupper stop for a rubber spring 315. The disc has a radius which is lessthan the radius of the cylinder 78. A flexible annular washer in theform of a rubber disc 319 is held concentrically on the shaft 81 abovethe disc 318. The washer 319 has a radius which is less than the radiusof the cylinder 78, but greater than that of disc 318. The washer ispreferably held against the disc by a retaining ring (not shown). Anannular foam accumulator 321 is positioned concentrically on the pistonshaft in the cylinder 78 between the upper end of the cylinder and thewasher 319.

The rubber washer 312 extends radially to contact the interior surfaceof the cylinder 78; the washer 313 extends radially to contact the innersurface of the floating piston 309; therefore, the hydraulic fluid 325can flow between the inner surface of the cylinder 78 and the perimetersof these washers. The inner bore 310 of the floating piston 309 has alarger diameter than the shaft 81. This allows the inside edges of thewashers 312 and 313 to curl and permit fluid to pass momentarily. Thepiston 309 will follow, due to the curling resistance of the washers,and reseat.

The neutral position of the piston shaft 81 with respect to the cylinder78 positions fixed and floating pistons 300 and 309 as illustrated inFIG. 4. In this regard, the floating piston 309 is positioned so thatits upper edge is just above the position-sensing port 86. This sealsthe port, preventing the introduction of the return potential into thecylinder 78. Assume now that a left-hand turn is begun, in which case,the cylinder and piston assembly 80 will expand, moving the pistonassembly 79 upwardly in the cylinder 78. Immediately, the solenoid valve35 is configured to provide the pressurizing potential through the upperport 83 and the return component through the lower port 85, tocounteract the upward displacement of the piston assembly 79. Now, thepressurizing potential presses downwardly on the floating piston 309.The net effect is to produce a downward correcting motion on thefloating piston 309. This moves the entire piston assembly 79 downwardlyuntil the combination of compression of the washer 307 and downwardmovement of the fixed piston 300 displaces floating piston 309downwardly by an amount sufficient to uncover the position sensing port86. At this point, the pressurizing potential component will be "shortcircuited" through the port 86, preventing any further downward movementof the piston assembly 79. When these correcting forces are removed, themechanical suspension of the automobile will move the piston assembly 79back to the unactivated, neutral position illustrated in FIG. 4.

Next, when the correction potentials are reversed so that the port 85 ispressurized and the return potential is provided in the port 83, the netpressure acting on the fixed piston 300 will move it upwardly, and withit the floating piston 309. As inspection of FIG. 4 will confirm, thefloating piston 309 must be displaced upwardly a significant distancebefore the port 86 is uncovered. However, before the floating piston canbe displaced by this distance, the floating piston in the right frontcylinder and piston assembly will have been displaced downwardly,thereby shorting the return to the pressurizing potential through theupper portion of the cylinder 71.

Assume now that the left front wheel encounters a bump, resulting in asudden displacement of hydraulic fluid upwardly through the port 300aand 300b of the fixed piston 300. The amount of flow is determined bythe ratio of the total area of the ports 300a and 300b to the totalsurface area of the upper face of the fixed piston 300 and ports 83, 85and flow into the upper portion of the cylinder. Displacement ofhydraulic fluid upwardly is transferred against the lower face of thefloating piston 309, resulting in a upward displacement of the floatingpiston against the force of the spring 315. Upward displacement of thefloating piston 309 causes the outward edge of the washer 319 to curlupwardly, which permits hydraulic fluid 325 to be displaced upwardlyinto the top of the cylinder 78. Displacement in this direction isabsorbed by compression of the foam 321. After upward displacement bythe bump, the cylinder and piston assembly 80 is returned to its neutralconfiguration of FIG. 4 by the mechanical suspension components,including the external springs 39a and b illustrated in FIG. 1, whichact between the body of the vehicle and the cylinder 78.

Next assume that the left front wheel 12 encounters a pothole. In thiscase, the cylinder 78 is pulled downwardly with respect to the pistonassembly 79. Now, the hydraulic fluid in the lower portion of thecylinder 78 is increased by flow through port 85 and moves downwardly,from the interior of the piston 300 as aided by expansion of the foam305. Simultaneously, hydraulic fluid is forced downwardly from the topof the cylinder 78; the downward displacement being accompanied bycompression of the foam 321. However, the displacement of fluiddownwardly past the washer 319 is relatively slower than upwarddisplacement past the washer 319 because downward curvature of thewasher is limited by the disc 318. The downward displacement of thehydraulic fluid acts against the floating piston 309 to keep it forcedagainst the rubber washer 307. Again, when the pothole is passed, theexternal mechanical suspension components of the vehicle return thecylinder and piston assembly of FIG. 4 to their neutral positions.

Sudden surges of hydraulic fluid in the system of FIG. 1 are dampened bythe damping mechanism of FIG. 5. The damping mechanism of FIG. 5consists of a cylinder 400 with a stationary annular disk 405 withthrough ports 407 and 409. A pair of valve springs 410 and 412 aredisposed on respective opposing faces of the annular disk 405. Spring140 has an opening 411 which communicates with the port 407; the spring412 has an opening 413 which communicates with the through port 409. Thespring constant of the springs 410 and 412 are substantially equal. Thedamping mechanism of 400 operates in much the same manner as the shockabsorbing element of the pistons in the front and rear wheel assemblies90 and 100 with the exception that the annular disk 405 does not move.In this regard, a sudden surge of hydraulic fluid into the port 420 willbe communicated through the port 407 against the spring 412. If thesurge is of sufficient magnitude, the spring 412 will be slightlydisplaced to permit displacement of fluid from the left to theright-hand side of the cylinder 400. Similarly, a surge of hydraulicfluid entering the cylinder 400 through the port 422 will be dampened bythe spring 410.

Refer now to FIGS. 6-9 for an understanding of the second embodiment ofthe invention in which numerals which are identical with the numerals inFIG. 1 indicate like parts. Thus, the schematically-represented systemof FIG. 6 is understood to be used in conjunction with a vehicleincluding a body, a frame, wheels, a suspension which connects the bodyto the wheels, and means for rotatably connecting the wheels 10, 12, 14,and 16 to the frame. The suspension is represented in part by springs39a-39b. In FIG. 6, there are a plurality of hydraulicly-actuatedcylinder and piston assemblies which include the assemblies 570, 580,590, and 600. The assemblies 570 and 580 are front wheel assemblieswhich are connected to the vehicle between the vehicle body and thefront wheels 10 and 12, respectively. The assemblies 590 and 600 arerear wheel assemblies which are connected between the vehicle body andthe rear wheels, 14 and 16, respectively. The cylinder and pistonassemblies are hydraulicly actuated to be alternately compressed orexpanded in response to the flow of hydraulic fluid.

The front wheel assembly 570 includes a cylinder in which is slidablydisposed a piston 572. The cylinder has upper and lower ports 574 and575 and a position-sensing port 576 which is normally closed to theupper and lower ports by the rest position of the piston 572.Identically, the cylinder and piston assembly 580 includes a cylinderwith a piston 579, upper and lower ports 583 and 585, respectively, anda position-sensing port 586 normally closed by the piston 579.

The rear cylinder and piston assembly 590 includes a cylinder with aslidable piston 593 and upper and lower ports 595 and 597, respectively.Identically, the rear wheel assembly 600 has a cylinder with a slidablepiston 603, an upper port 605, and a lower port 607.

A differential hydraulic signal is provided from a pumped source (notshown) by way of a valve 535 which is identical in structure andoperation with the valve 35 of FIG. 1. Further, the valve 535 isoperated by a control means (not shown) identical in all respects withthat illustrated in FIG. 2. Thus, the valve operates in response to avehicle turn by outputting a differential hydraulic signal includingpressure (P) and return (R) potentials which indicate the direction ofthe vehicle turn as discussed above with reference to the valve 35 ofFIG. 1. One output of the valve 535 is connected to the lower port 575of the assembly 570 by a hydraulic connection 700. Hydraulic connection702 connects the other output of the valve 535 to the lower port 585 ofthe assembly 580. The position-sensing ports 576 and 586 are connectedby hydraulic lines 704 and 705 to a common point 708 which is connectedthrough a back pressure valve 710 to the return potential R of thehydraulic pump (not shown).

On a first (right) side of the vehicle, the cylinder and piston assemblypairs 570 and 590 are interconnected through upper port 574 and lowerport 597 by a hydraulic line 720, accumulator 710, identical inconstruction to accumulator 723. The upper ports 595 and 605 of the rearwheel cylinder and piston assemblies are interconnected by hydraulicline 722, accumulator 723, and hydraulic line 724. The circuit iscompleted by hydraulic line 726, and accumulator 711, which connects theports 607 and 583 of the pair of cylinder and piston assemblies 600 and580, respectively, on the second (left) side of the vehicle.

Assume now that the vehicle with the anti-roll system illustrated inFIG. 6 makes a left-hand turn, in which case the right-hand side of thevehicle will incline downwardly with respect to the left-hand side ofthe vehicle. This is referred to as "roll". Additionally, the front endof the vehicle will incline downwardly with respect to the rear, whichis referred to as "pitch". In this case, the rolling force on thevehicle is counteracted by expansion of the cylinder and pistonassemblies 570 and 590 and by compression of the cylinder and pistonassemblies 580 and 600. The valve 535 will be configured to deliver thepressurizing potential of the hydraulic signal through the hydraulicline 700 to the lower port 575 of the assembly 570, while the returnpotential is provided to the lower port 585 of the assembly 580 throughthe hydraulic line 702.

Considering now the components on the right-hand side of the automobile,the pressurizing potential introduced through the port 575 will move thepiston 572 upwardly, forcing fluid out of the upper port 574 through theconductor 720 and into the bottom port 597 of the rear assembly 590.This will move the piston 593 upwardly. Upward movement of the pistons572 and 593 will provide an erecting force on the right-hand side of thevehicle to counteract the downward inclination induced by the rollingforce of the left-hand turn.

To complement the expansion of the assemblies 570 and 590, theassemblies 580 and 600 on the left-hand side of the vehicle will becompressed by the return potential delivered to the lower port 585.Under the influence of the return potential, the piston 579 will movedownwardly drawing hydraulic fluid into the assembly via 583, 726, 607.Extraction of the fluid from the bottom of the assembly 600 will causethe piston 603 to move downwardly. The downward movement of the pistons579 and 603 will compress the assemblies 580 and 600, therebycounteracting the upward inclination of the left-hand side of thevehicle during a left-hand turn. The connection 722, 723, 724 betweenthe upper ports 595 and 605 of the rear assemblies 590 and 600 permitsthe exchange of fluid between those assemblies. During the left-handturn just described, the hydraulic fluid will flow from the assembly 590to the assembly 600.

In response to a right-hand turn, the valve 535 will be configured toprovide the pressurizing potential of the hydraulic fluid signal to thelower port 585 and the return potential to the lower port 575. In thiscase, the actions of the cylinder and piston assemblies will be thereverse of that just described.

Refer now to FIGS. 7A and 7B for an understanding of the structure andoperation of the front wheel cylinder and piston assemblies 570 and 580.FIG. 7A illustrates only the assembly 570, with the understanding thatthe assembly 580 is identical in all respects.

As the cross-section drawing of FIG. 7A illustrates, the front wheelcylinder and piston assembly 570 includes a piston 572 which is slidablewithin the cylinder. The piston 570 is connected by a piston rod 730 tothe body of the automobile by conventional means. The piston includes apiston body 732 with radially-spaced, axially-extending bores 733a,733b. Although only two bores are shown in the Figure, it is understoodthat more may be provided in cross-sectional planes not shown. One endof each bore is flared radially to provide a fluid passage around theend of a disk. The bore 733a is flared at the top of the piston so thatfluid can flow from the upper portion of the cylinder, around the edgeof the disk 749, into the bore. The bore 733b is similarly flared at thebottom of the piston to provide a fluid passage around the edge of thedisk 749. An annular teflon piston ring 735 encircles an indented outersurface of the piston 572. The piston 572 is attached to the rod 730 byan arrangement which includes a threaded nut 737, a washer 738, and twoO-rings 739a and 739b, and the disk 740. The top of the piston isretained on the rod by an arrangement including a retaining ring 743, awasher 745, an O-ring 747 and a disk 749. The disks 740 and 749 cancomprise conventional valve springs which operate as described abovewith regard to the valve springs 207 and 210 illustrated in FIG. 3. TheO-rings 739a and b and 747 act essentially as springs and compress inresponse to movement of the plates 740 and 749, respectively.

A lower floating piston 753 seals the bottom of the cylinder 570. Thelower floating piston is generally cylindrical with an upper portion 755in which is cut an annular slot 756. An O-ring 758 in the slot 756provide a fluid seal which retains the hydraulic fluid in the cylinder570. The bottom portion of the floating piston 753 has a rectangularslot which is completely occupied by three rubber cylinders made ofO-ring material (759a, 759b, and 759c). Two of the rubber cylinders arebeneath the bolt, while one is positioned above it. Holes are cutdiametrically at the bottom of the cylinder 570 so that the floatingpiston 753 can be retained at the bottom of the cylinder by the elongatebolt 760 and nut 761.

Positioned above the piston 572 is an upper floating piston assemblyincluding a rubber spring 762 having a through bore through which thepiston rod 730 extends. Above the rubber spring 762 an annularcup-shaped floating piston 763 having a cylindrical cut-out centerportion with a bottom surface 764 which contacts the upper end of therubber spring 762. A pair of 90-degree through-ports 765a and 765b arecut through the surface 764 from which they extend upwardly until making90-degree turns. The upper ends of the through ports 765a and 765b aresealed by an O-ring 767 seated in an annular groove in the upper portionof the floating piston 763. The cup-shaped floating piston 763 has anaxial bore through which the piston rod 730 extends and the piston isfree to move on the rod. A stopping O-ring 768 is placed on the rod 730between the upper inner surface of the cylinder 570 and the uppersurface of the floating piston 763. The largest diameter of the floatingpiston 763 is less than the inner diameter of the cylinder 570,affording a fluid path between the inner surface of the cylinder 570 andthe piston's extreme outer surface. Fluid is able to travel in eitherdirection on this path. Uni-directional fluid paths are affordedupwardly through the through-bore 765a and 765b. When fluid pressure istransferred in this direction, the O-ring 767 will give outwardlyslightly to open these passages. However, fluid flowing against theO-ring 767 from within the upper portion of the cylinder will only seatthe ring more tightly against the bores 765a and 765b, preventing fluidflow downwardly through these passages.

When an automobile to which the cylinder and piston assembly 570 hasbeen mounted is normally loaded and at rest, the lower end of the piston572 occupies a position between the position sensing port 576 and thelower port 575. When a pressurizing potential is introduced through thebottom port 575 to expand the cylinder and piston assembly 570, thepiston 572 moves upwardly in response to the pressurizing potentialuntil the position-sensing port 576 is uncovered. When this occurs, thepressurizing potential is returned through the port 576, therebypreventing any further roll correction. When the pressurizing signal isremoved, the cylinder 572 returns to its rest position where its lowerend is positioned between the ports 575 and 576.

Tilt limitation as practiced in the second embodiment of the anti-rollsystem, which is illustrated in FIG. 7, is enabled in response toexpansion of the front wheel cylinder and piston assemblies. Thiscontrasts with the operation of the front wheel cylinder and pistonassemblies in the first embodiment. As explained above and as referenceto FIG. 4 shows, tilt limitation in the first embodiment is activated inresponse to compression of the front wheel cylinder and pistonassemblies. In practice, the requirements and circumstances of anapplication will determine which of these embodiments is the best modeof practicing the invention. The inventor has found that, all thingsbeing equal, the cylinder and piston assembly used in the secondembodiment provides a certain advantage. In many applications, when avehicle is loaded with passengers or freight, a portion of the addedload is applied to the cylinder and piston assemblies of the anti-rollsystem. In the first embodiment, this results in compression of thefront wheel cylinder and piston assemblies which moves the top surfaceof the piston toward the position sensing port. This reduces the amountof roll correction that the first embodiment can introduce until tiltlimitation occurs. In contrast, compression of the cylinder and pistonassembly illustrated in FIG. 7 will move the lower surface of the piston272 downwardly, thereby increasing the amount of roll compensation whichthe second embodiment will provide before tilt limitation occurs.

The combination of the disks 740 and 749 with the through-bores in thepiston 572 provides shock absorption substantially as described abovewith reference to FIG. 3. The difference is that shock displacement ofthe piston causes fluid to flow around the edge of a disk, through theflared end of a through bore and against the disk at the other end ofthe through bore. Use of the O-rings 739 and 747 to transfer retainingforce to the disks 740 and 749 affords a low-cost, reliable springaction which opposes movement of the disks in response to fluiddisplacement in the cylinder and piston assembly 570. Thus, for example,assuming that the front wheel where the assembly 570 is mounted hits abump, the assembly 570 will undergo a short, sharp compression which isaccommodated by movement of hydraulic fluid around the disk edge throughthe bore in the cylinder 733b against the disk 749. The disk 749 willtransfer the shock force in response to which the O-ring 747 willcompress. When the O-ring compresses, the disk moves away from the hole,permitting fluid to flow through it. As the shock impulse dies, thecompression of the O-ring will assist in returning this disk 749 to aposition covering the bore 733b. The two O-rings 739a and b providestiffer resistance against rebound than does the single O-ring 747against jounce.

The upper floating piston assembly also affects shock absorption in thefront wheel cylinder and piston assemblies. In this regard, if the frontwheel to which the assembly in FIG. 7A is attached encounters apot-hole, the assembly of FIG. 7A is expanded sharply. The sharpexpansion is accommodated by hydraulic fluid flow downwardly through thethrough bore 733a of the piston 572. Upward movement of the piston 572also moves the upper floating piston assembly upwardly until the O-ring768 encounters the upper interior surface of the cylinder 570. When thisoccurs, the upward movement of the piston 572 is damped and reduced bythe compression of the rubber spring 762 against the surface 764 of theupper floating piston 763.

The lower floating piston 753 confers an unexpected result in operationof the anti-roll system. Refer now to FIGS. 7A and 7B. When the upperend of the rod 730 is attached to the vehicle body with a solid bushingand low profile tires are mounted to the vehicle frame, the surface ofthe road on which the vehicle travels is "transferred" to the cylinderand piston assemblies of the anti-roll system. Relatedly, as bumps andholes are encountered, sudden upward and downward displacement of thewheels tends to cause related compression and expansion of the cylinderand piston assemblies. The road envelope is absorbed to some extent inconventional shock absorbing pistons by using a rubber bushing inmounting the piston to the vehicle body. In this case, the bushingabsorbs some of the impulse displacement transferred to the cylinder andpiston assembly from the road surface. A solid bushing will not providethis absorption. However, in the assembly of FIG. 7A, the impulseresponse to bumps and potholes in the road surface is partially absorbedby the lower floating piston. As the piston 572 responds to the randomimpulses in the surface of the road by the shock absorbing actiondescribed above, the surges which this action produces in the hydraulicfluid are absorbed by upward and downward translation of the lowerfloating piston 755 on the rubber cylinders 759 about the center line ofthe stationary bolt 760. The inventor has found that this floatingpiston configuration significantly suppresses the audible response ofthe cylinder and piston assemblies of an anti-roll system to roadsurface effects. Further, with two rubber cylinders beneath the bolt,and one above it, the floating piston yields more in response to reboundthan to jounce.

The rear wheel cylinder and piston assemblies are equivalent and theassembly 590 is illustrated in, and explained with reference to, FIG. 8.The assembly 590 includes a moveable piston 593 which slidesreciprocally within the cylinder in response to movement of hydraulicfluid through the ports 595 and 597. Sustained, low frequency fluidtransfer through these ports results from provision of the differentialfluid signal provided through the valve 535. This response has alreadybeen explained. The rear wheel cylinder and piston assemblies alsoprovide shock absorption in these fixed pistons with an arrangementvirtually identical with that employed in the front wheel cylinder andpiston assemblies. Such shock absorption is provided through the piston593 which is mounted to the piston rod 770 between a threaded nut 771and a retaining ring 776. Nut 771 thrusts against a washer 773 and anO-ring 775 which holds an annular disk. Similarly, at the top of thepiston, retaining washer 777 transfers retaining force through an O-ring778 to a valve spring with holes which match selected bores through thepiston 593. This arrangement provides shock absorption response for theassembly 590 as explained above for the front wheel assemblies.

The assembly 590 also includes an upper floating piston assembly 780which operates identically to the upper floating pistons of the frontwheel assemblies. The upper floating piston assembly includes a rubberspring 781, a cup-shaped floating piston 782 with a sealing O-ring 783and a stopping O-ring 784.

The rear assembly 590 also includes a lower cylindrical portion 800which is in perpendicular fluid communication with the cylinder 590. Alower, cup-shaped floating piston 801 is slidably disposed in theextension 800 and is retained therein by an O-ring 802 and a retainingpiston 803 having an annular O-ring 804 which hydraulically seals theextension 800. The piston 803 is retained in the extension 800 by aretaining ring 805. The lower floating piston 801 is filled with a foamaccumulator material 806. A rubber spring 807 is disposed between theinterior surface of the cylinder 590 and the back of the lower floatingpiston 801. The diameter of the lower floating piston 801 is slightlyless than the interior diameter of the extension 800, and radial throughbores 808 complete a fluid path along the side of the lower floatingpiston 801 into its interior.

In operation, the lower floating piston assembly assists in shockabsorption. In this regard, when a pot-hole is encountered by a rearwheel, the real wheel cylinder and piston assembly of FIG. 8 expands,with the piston 593 moving upwardly with respect to the cylinder. Thispulls a vacuum in the lower portion of the cylinder beneath the piston593 which causes the lower floating piston 801, the O-ring 802, and thesealing piston 803 to move inwardly against the rubber spring 807. Whenthe riding surface again levels, the compression in the rubber spring807 returns the floating piston, O-ring, and sealing piston against theretaining ring 805. When a bump is encountered, and the piston 593 movesdownwardly in the cylinder, hydraulic fluid is displaced downwardly inthe cylinder toward the floating piston assembly. This downward movementis dampened when the fluid flows between the outer surface of thefloating piston 801 and the extension 800, through the radial throughbores 808 against the foam accumulator 806. The accumulator 806compresses in response to the downward movement of the hydraulic fluidand expands when the bump is passed and the riding surface is once againlevel.

With this description of the construction and operation of the front andrear cylinder and piston assemblies, consider again the operation of thesecond embodiment of FIG. 6 in response to a left-hand turn. Inleft-hand turn, the combined roll and pitch makes the outside front ofthe automobile tend to dip, while the outside rear of the automobiletends to rise. This tends to compress the right front assembly 570 andexpand the rear left assembly 600. In response to the turn, thepressurizing potential is introduced through port 575 of the frontassembly 570 while the return potential is connected to the port 585 ofthe front assembly 580. Refer now to FIGS. 7A and 8. Introduction of thepressurizing potential at port 575 causes a shock-like impulse whichincreases the pressure at the bottom of the piston 572. The pressurepushes the piston upward in the cylinder, thereby expanding the assemblyin reaction to the compression exerted by the turn forces. Some of theshock-like impulse caused by the introduction of the return potentialthrough the port 575 is transferred upwardly through the through port733b of the piston 572 around the sides and through the through ports ofthe upper floating piston assembly and out the upper port 524 of thefront wheel assembly 570. The pressurizing potential is maintainedthrough the upper port 524 until the position-sensing port 576 isuncovered.

For so long as the pressurizing potential is provided through the upperport 524, the right rear assembly 590 is activated by introduction ofthe pressurizing potential through the lower port 597. The initialimpulse of the pressurizing potential is transferred through the fixedpiston 593 and the floating piston out the upper port 595 of the rearassembly. Pressurizing potential is introduced through the upper port605 of the left rear assembly 600 where it exerts a downward force onthe upper floating piston assembly and fixed piston of the left rearassembly. As FIG. 8 shows, the full pressurizing potential introducedthrough the port 595 is brought against the top of the fixed piston 593by flow of fluid around the sides of the floating piston and bycompression of the rubber spring 781 by downward movement of thefloating piston 782. This exerts an immediate compressing action on theleft rear assembly which tends to lower the inside rear corner of theautomobile during a left-hand turn.

In FIG. 9, the back pressure valve 710 is illustrated. The valveconsists of a bored, substantially cylindrical member having hydraulicports 485 and 487 which connect conventionally to hydraulic conductors.A spring-loaded valve 791 is disposed in an inner chamber 790 of thevalve. The valve 791 is loaded by a spring 792 which seats the valve 791to close the opening 793 when the differential hydraulic signal isabsent. When the signal is applied to the system, the pressure keeps thevalve opened. Surges of the hydraulic fluid in the anti-roll system ofFIG. 7 are damped by displacement of the internal valve 791 against thespring 792. When the surge expires, the spring 792 returns the valve toits partially-open position.

Returning to FIG. 6, hydraulic fluid surges in the anti-roll system ofFIG. 6 are also damped by an accumulator 723 (which is shown incross-section in FIG. 6) connected between the rear cylinder and pistonassemblies. The accumulator 723 is a hollow elongate cylinder withhydraulic coupling ports 795 and 796. The ports 795 and 796 areconventionally coupled to the hydraulic line 722 and 724. Disposed inthe cylinder is an air-filled bladder 799 made of a flexible material.The hydraulic fluid used in the system is incompressible when comparedto the air which fills the bladder 799. Thus, when a surge occurs in thehydraulic fluid in the upper portions of the rear wheel cylinder andpiston assemblies, some of the force of the surge is transferred againstthe outer surface of the bladder 799. Since the air which fills thebladder 799 is relatively compressible, some of the force of the surgewill be absorbed by compression of the bladder. When the surgedissipates, the bladder expands to an equilibrium volume forcing fluidback up through the piston. Fluid resistance in the lines connecting theaccumulator 723, 710, and 711 are turned to serve in the damping processof medium frequency bumps.

In the first and second embodiments of the anti-roll system illustratedand disclosed above, tilt limitation is provided through the positionsensing ports of the front wheel cylinder and piston assemblies. Ineither embodiment, provision of tilt limitation on each side of avehicle permits a smooth and fast response to vehicle turns. While bothembodiments show provision of tilt limitation in the front wheelcylinder and piston assemblies, this is not intended to limit provisionof tilt limitation in other cylinder and piston assemblies of ananti-roll system. Further, while, in each embodiment, tilt limitation isactivated in response to compression but not expansion, or to expansionbut not compression, a need may arise where tilt limitation would beactivated in response to compression of one set of assemblies and toexpansion of another set of assemblies.

Another feature which produces an unexpected result in this inventioncan be appreciated with reference to FIGS. 7A and 8. Assuming equaldiameters for the cylinders of the assemblies 570 and 590, the inventorhas found that providing a piston rod 730 having a larger diameter (d₁)than the diameter (d₂) of the piston rod 770 will accelerate theresponse of the front wheel cylinder and piston assemblies to adifferential hydraulic signal, compared with the response of the rearwheel assemblies. The larger diameter of the front wheel assemblyreceiving the pressurizing signal means that a larger surface area willbe presented to the portion of the signal which is transferred by theshock absorbing design of the piston. The larger surface area willintegrate more of the pressurizing force, thereby "boosting" theexpansion of the outside front assembly. This "boost" will counteractthe tendency of the inside rear wheel to lift off of the road surface,and suppress any tendency which the vehicle may have to oversteer duringa turn.

Finally, all of the hydraulic lines which interconnect the elements ofthe anti-roll system of this invention can be made of a flexiblematerial, which will increase the damping of the system to surges in thehydraulic fluid.

With this description, it should be evident to those skilled in the artthat my invention can be practiced other than as described above,without departing from the spirit of these teachings.

I claim:
 1. A cylinder and piston assembly comprising:a cylinder withupper and lower ports, each of the ports opening into the interior ofthe cylinder; a piston means slideably contained within said cylinderfor reciprocal, hydraulically-actuated movement within said cylinderbetween said ports; a first piston port opening between each end of saidpiston means, a first port cover attached to a first end of said pistonmeans and biased against said first end of said piston means to coverone end of said first port, a second piston port opening between eachend of said piston means, and a second port cover attached to saidsecond end and biased against said second end to cover one end of saidsecond port; a floating piston assembly sealing said cylinder beneathsaid lower port, said floating piston assembly being contained in theinterior of said cylinder and attached to said cylinder for reciprocalmovement therein.
 2. The shock absorbing cylinder of claim 1 whereinsaid floating piston assembly is resiliently biased against reicprocalmovement in said cylinder.
 3. The shock absorbing cylinder of claim 2wherein said floating piston assembly is resiliently baised to a greaterdegree against movement of said piston means away from said lower portthan against movement of said piston means toward said lowr port.
 4. Theshock absorbing cylinder of claim 1 wherein the said floating pistonassembly includes:a substantially cylindrical piece with an annularindentation for providing a liquid seal between the floating piston andthe interior of the cylinder; a through-bore extending diametricallythrough said cylinder; and a flexible bushing disposed in the diametricbore flexibly seating the floating piston assembly in the cylinder. 5.The shock absorbing cylinder of claim 4 wherein said floating pistonassembly is reciprocally mounted in said cylinder by a fastenerextending diametrically through said cylinder and said through-bore. 6.The shock absorbing cylinder of claim 5 wherein said flexible bushingincludes a first bushing extending in said through-bore on a first sideof said fastener and a second bushing extending in said through-bore ona second side of said fastener, said second flexible bushing beingthicker than said first flexible bushing.
 7. The shock absorbingcylinder of claim 6 wherein said first flexible bushing is formed from arubber cylinder and said second flexible bushing is formed from tworubber cylinders.
 8. The shock absorbing cylinder of claim 1 furtherincluding a second floating piston disposed in said cylinder betweensaid piston means and said upper cylinder port, said second floatingpiston being slideably mounted for reciprocal movement within saidcylinder on a piston rod extending axially in said cylinder, andresiliently biased away from said piston means.
 9. The shock absorbingcylinder of claim 8 wherein the second floating piston includes lateralthrough-ports and a resilient seal covering said through-ports.
 10. Theshock absorbing cylinder of claim 9 wherein the second floating pistonincludes a resilient stop between said second floating piston and an endof said cylinder.
 11. The shock absorbing cylinder of claim 10 whereinsaid resilient seal permits only uni-directional fluid flow through saidthrough-bore.
 12. The shock absorbing cylinder of claim 1 wherein saidpiston means port covers are rigid disks and are resiliently biasedagainst the ends of said piston means by resilient biasing elements. 13.The shock absorbing cylinder of claim 12 wherein the resilient biasingforce on the port cover at said first end of said piston means isgreater than the biasing means on the port cover of said second end ofsaid piston means.
 14. The shock absorbing cylinder of claim 1 furtherincluding:a second cylinder mounted to said first cylinder below saidlower port and having an interior extending to the interior of saidfirst cylinder.
 15. The shock absorbing cylinder of claim 1 wherein saidfloating piston includes a piston head surface facing toward said lowerport and an interior containing an accumulator material, said interiorextending from an open end of said floating piston in communication withthe interior of said cylinder.
 16. The shock absorbing cylinder of claim15 wherien said floating piston is resiliently biased away from saidcylinder.
 17. The shock absorbing cylinder of claim 16 wherein saidfloating piston includes a resilient stop between said floating pistonand a lower end of said cylinder.
 18. A cylinder assembly comprising:acylinder having a fluid containable interior defined by a first end, asecond end and a generally cylindrcal wall extending between said firstand second cylinder ends; damping means slideably contained within saidcylinder for reciprocal movement within said cylinder between said firstand second cylinder ends; and at least one of said cylinder ends beingslideably mounted within said cylinder for reciprocal movement withinsaid cylinder relative to the other cylinder end.
 19. The cylinderassembly of claim 18 wherein said slideable cylinder end includesdamping means.
 20. The cylinder assembly of claim 18 wherein saidslideably cylinder end includes a floating piston assembly having meansfor resiliently biasing said piston assembly against reciprocal movementwithin said cylinder.
 21. An actuator system, comprising:a cylinderhaving a fluid containable interior defined by a first end seal, asecond end seal and a generally cylindrical wall extending between saidfirst and second cylinder ends; a primary damper slideably containedwithin said cylinder for reciprocal movement within said cylinderbetween said second cylinder end seals; and a secondary damper providingone of said end seals, said secondary damper providing fluid dampingrelative to said primary damper.